Frequency multipliers and methods for frequency multiplication

Abstract

A frequency multiplier that has the following characteristics: a phase generator (50, 102) configured to receive an oscillation signal (56) and to provide phase-shifted versions of the oscillation signal (56) at phase generator outputs (60, 62, 64); an injection-synchronized ring oscillator (52, 104) having a plurality of stages (70, 72, 74), wherein each of the phase generator outputs (60, 62, 64) is coupled to a different stage of the plurality of stages (70, 72, 74) for the purpose of multi-point injection, and a combiner (54, 106) configured to combine output signals of the plurality of stages (70, 72, 74) of the injection-synchronized ring oscillator (52, 104) into a signal (78) whose frequency is a multiple of a frequency of the oscillation signal (56).

Description

Area

[0001] The present application relates to a frequency multiplier and a method for frequency multiplication, and in particular to a frequency multiplier and a method for frequency multiplication for generating an output signal whose frequency is a multiple of the frequency of an oscillation signal. background

[0002] In general, a frequency multiplier is an electronic circuit that generates an output signal whose output frequency is a multiple of its input frequency. For example, in any communication / radar system, if the frequency of a local oscillator is lower than a desired carrier frequency, a frequency multiplier can be used to generate the carrier frequency from the local oscillator's frequency. The frequency multiplier produces the desired frequency f at its output. out = N·f lo , where fout the desired output frequency is f lo The frequency of the local oscillator is given by f, and N is the multiplication factor. Ideally, the multiplier only generates a signal at f. out one harmonic and suppresses all other harmonics with infinite harmonic blocking. In practice, this may not be true, and together with the desired harmonic f out Several or all harmonic multiples of f lie lo in the output signal if no further measures are taken regarding harmonic suppression.

[0003] A first, common approach to achieving high harmonic suppression in a frequency multiplier is in Fig. Figure 7 shows a voltage-controlled oscillator (VCO) 10 generating a differential output signal 12 with an oscillation frequency f. loThe differential output signal 12 is provided to a frequency multiplier 14. The frequency multiplier 14 generates an output signal 16 at its output with a frequency that is the frequency of the input signal multiplied by a multiplication factor N. The multiplication factor N can be a natural number greater than or equal to 2. The output of the frequency multiplier 14 is connected to the input of a bandpass filter stage 18 cascaded with the multiplier. The passband of the bandpass filter stage is at f out = N·f locentered, and therefore the bandpass filter stage blocks the other harmonics. Thus, an output signal in which the harmonics are suppressed is achieved at output 20 of the bandpass filter stage. However, to achieve a high harmonic blocking factor, a filter with a high Q factor is desirable. Such a filter is difficult to implement, and even if such a filter is implemented, it is difficult to maintain the passband at f over process, voltage, and temperature fluctuations (PVT fluctuations, PVT = process, voltage, temperature). out to center. Furthermore, at RF / MMW frequencies (RF = high frequency, MMW = millimeter wave), the bandpass filter would be an LC resonator, and thus the blocking would be limited by the order of the filter.

[0004] Fig. Figure 8 shows another common solution approach for harmonic blocking. As in Fig. As shown in Figure 8, the output of the frequency multiplier 14 has an injection locking stage 22, which provides a signal at f out The oscillator is coupled to the running oscillator. The oscillator can be an LC-VCO (VCO = voltage-controlled oscillator). The positive feedback behavior of the injection synchronization stage 33 helps to block the harmonics in order to produce an output signal with a frequency f. out = N·f lo to output at an output 24 of the injection synchronization stage 22. However, in order to achieve proper synchronization, the freewheeling frequency of the LC-VCO must be as close as possible to f outThis is difficult to achieve due to process, voltage, and temperature fluctuations. Furthermore, the harmonic blocking behavior of the LC-VCO is high within the synchronization range, but limited to the bandpass behavior of the LC-VCO resonant circuit outside of the synchronization range. Since the synchronization range is typically narrow, with typical values ​​for LC-VCOs around 15%, harmonic blocking is limited.

[0005] Frequency multipliers are described in US 2016 / 0373094A1. One example of a frequency multiplier includes a phase generator and a combiner. Another example includes a ring oscillator and a combiner.

[0006] Accordingly, there is room for improvement in achieving high harmonic suppression across process, voltage and temperature fluctuations and over a wide input frequency range. Brief description

[0007] Examples of the present disclosure provide a frequency multiplier comprising a phase generator configured to receive an oscillation signal and to provide, at phase generator outputs, versions of the oscillation signal that are phase-shifted relative to each other. The frequency multiplier comprises an injection-synchronized ring oscillator having a plurality of stages, each of the phase generator outputs being coupled to a different stage of the plurality of stages for the purpose of multi-point injection. The frequency multiplier further comprises a combiner configured to combine output signals of the plurality of stages of the injection-synchronized ring oscillator into a signal whose frequency is a multiple of a frequency of the oscillation signal.

[0008] Examples of the present disclosure provide a frequency multiplication method comprising generating versions of an oscillation signal that are phase-shifted relative to each other, multi-point injection synchronization of a ring oscillator using the generated versions of the oscillation signal, and combining output signals of stages of the ring oscillator to form a signal whose frequency is a multiple of a frequency of the oscillation signal.

[0009] Thus, in examples from the present disclosure, the ring oscillator can correct phase errors in the phase-shifted versions of the oscillation signal over process, voltage, and temperature variations and, thanks to multi-point injection, over a wide frequency range. Therefore, the signals subsequently combined can have equal phase spacing, and the combiner can generate an output signal at its output with a frequency that is a specific multiple of the input frequency with high harmonic suppression. Brief description of the drawings

[0010] Examples of the revelation will now be described using the accompanying drawings, in which: Fig. 1 shows a schematic diagram of a frequency multiplier according to an example of the present disclosure; Fig. 2 shows a schematic diagram of a frequency multiplier according to another example of the present disclosure; Fig. 3 shows a schematic diagram of a phase generator; Fig. Figure 4 shows a schematic diagram of an example of a stage of an injection-synchronized ring oscillator; Fig. 5 shows a schematic diagram of an example of a combiner; Fig. 6 shows a flowchart of an example of a frequency multiplication process according to the present disclosure; Fig. Figure 7 shows a schematic diagram of a common approach to harmonic blocking; and Fig. Figure 8 shows a schematic diagram of another common approach to harmonic blocking. Detailed description

[0011] Examples of the present disclosure are described in detail below with reference to the accompanying drawings. It should be noted that the same elements, or elements having the same functionality, are designated with the same or similar reference numerals, and that it is customary to avoid repeating descriptions of elements designated with the same or similar reference numerals. Thus, descriptions of elements with the same or similar reference numerals are interchangeable. Many details are set forth below to provide a more thorough explanation of examples of the disclosure. However, it will be obvious to those skilled in the art that other examples can be implemented without these specific details.In other cases, well-known structures and devices are shown in block diagram form rather than in detail, in order to avoid obscuring the examples described herein. Furthermore, features of the various examples described herein may be combined unless otherwise specified.

[0012] Fig. Figure 1 shows an example of a frequency multiplier comprising a phase generator 50, an injection-synchronized ring oscillator 52, and a combiner 54. The combiner 54 is configured to receive an oscillation signal 56. The oscillation signal 56 can be generated by a local oscillator. In some examples, the oscillation signal 56 has a varying frequency. In others, the oscillation signal 56 is a frequency-modulated signal, such as a local oscillator signal used to generate frequency ramps in a frequency-modulated continuous wave (FMCW) radar system.

[0013] The phase generator 50 is configured to generate phase-shifted versions of the oscillation signal 56 at phase generator outputs 60, 62, and 64. In some examples, the phase generator 50 has N phase generator outputs, where N is an integer equal to or greater than 2. In some examples, N is a natural number equal to or greater than 3. In the example in Fig. In the example shown, N is 3. In general, the phase generator 50 is configured to generate a set of N signals by producing one signal for each integer j such that 0 ≤ j ≤ (N - 1). Each signal in the set has the same frequency and approximately the same amplitude and a phase equal to (360 / N)·j degrees.

[0014] The injection-synchronized ring oscillator 52 has a number of stages, wherein in Fig. Figure 1 shows three stages 70, 72, and 74. Of course, the injection-synchronized ring oscillator can have a different number of stages in other embodiments. In these examples, the injection-synchronized ring oscillator has N stages, where N corresponds to the number of phase generator outputs, i.e., the number of phase-shifted versions of the oscillation signal generated. Each of the phase generator outputs 60, 62, and 64 is coupled to a different stage 70, 72, and 74 of the ring oscillator for the purpose of multi-point injection. In contrast to classical single-point injection, where an output phase of the phase generator output is injected into the ring oscillator 52, multi-point injection injects a phase-shifted version of the signal into each ring oscillator stage (cell). Therefore, the injection synchronization bandwidth has a much wider frequency, and correct operation (i.e.,(a phase correction) is provided. In examples, a current corresponding to the respective generated version of the oscillation signal is injected into the respective stage of the injection-synchronized ring oscillator to achieve multi-point injection synchronization. An output of each stage of the ring oscillator 52 is coupled to an associated input of the combiner 54. The combiner 54 is configured to combine output signals of stages 70, 72, and 74 of the injection-synchronized ring oscillator 52 into an output signal 78 whose frequency is a multiple of the frequency of the oscillation signal.

[0015] In examples, the phase generator 50 has N phase generator outputs 60, 62, 64, where the generated versions of the oscillation signal are phase-shifted by 360 degrees / N relative to each other, when the injection-synchronized ring oscillator has N stages 70, 72, 74. After combining the respective output signals of the N stages, a signal with an N-fold frequency of the oscillation signal is generated. In examples, the frequency of the output signal is an integer multiple of the frequency of the oscillation signal.

[0016] In some embodiments, the oscillation signal is a differential signal, meaning it consists of two signals with a phase difference of 180 degrees. In such examples, the signal processing is differential signal processing. Consequently, in these embodiments, the phase generator is a differential phase generator, the phase generator outputs are differential phase generator outputs, the injection-synchronized ring oscillator is an injection-synchronized differential ring oscillator, and the combiner is a differential combiner. In other words, the corresponding circuits are configured to process differential signals. In other examples, the oscillation signal may be an asymmetric signal, and the respective electronic circuits are configured to process asymmetric signals.

[0017] Examples of the present disclosure are described below with reference to differential signals. However, it is understood that corresponding circuits can also be configured to process asymmetric signals.

[0018] Examples of the present disclosure provide a signal generator comprising a frequency multiplier and an oscillator 80 (with dashed lines in Fig. (as shown in Figure 1). Oscillator 80 can be a local oscillator. Oscillator 80 is configured to generate the oscillation signal 56. Oscillator 80 generates the oscillation signal 56 with a frequency f. lo As explained above, the oscillator 80 can be a voltage-controlled oscillator configured to provide a frequency-modulated oscillation signal, for example, an oscillation signal that has a frequency ramp.

[0019] Fig. Figure 2 shows an example of a signal generator comprising a frequency multiplier 100 and an oscillator 80. The oscillator 80 can be a local oscillator (LO). The oscillator 80 outputs an oscillation signal 56 (LO signal) at frequency f. lo off, and the oscillation signal 56 is fed into a phase generation block 102, which generates N differential phases at the frequency f loThe outputs of the phase generation block 120 are coupled to the inputs of N differential ring oscillator stages of a ring oscillator 104. The N differential output phases of the phase generation block 102 are used to synchronize the ring oscillator 104 of N differential stages. The outputs of the N differential ring oscillator stages are coupled to the inputs of a differential edge combiner 106. The N differential ring oscillator stages generate N differential signals at the outputs of the ring oscillator, and the N differential signals at the outputs of the ring oscillator are combined by the differential edge combiner 106 to produce the desired output frequency f at an output 108 of the frequency multiplier 100. out = N·f lo to obtain.

[0020] Accordingly, the present disclosure can be viewed as a combination of three blocks, i.e., phase generation is followed by an injection-synchronized ring oscillator and a slope combiner. In examples, the generation of N differential phases is followed by an injection-synchronized differential ring oscillator and a differential slope combiner. Examples of the present disclosure improve performance, as described below. Combining N signals that are equally spaced with respect to phase is an efficient way to implement a frequency multiplier by a factor of N. To perform a multiplication by N, N differential signals spaced 360 degrees / 2N apart can be combined. For example, to perform a multiplication by a factor of three (multiplication by three), three differential signals spaced 120 degrees apart can be combined.The harmonic suppression of the frequency multiplier output is directly proportional to the quality of the phases at the input of the combiner, for example, the edge combiner. If the signals have perfectly equal phase spacing, the harmonic suppression is infinite, and a single harmonic is at N·f. lo appears in the output spectrum. If the phases of the signals are not evenly spaced, harmonics appear at multiples of f. loin the output spectrum. To generate the signals at the input of the combiner, the phase generator and the injection-synchronized ring oscillator are used. A trade-off exists between the quality of the phases generated over a defined bandwidth and the loss. According to the present disclosure, the phase generation block is cascaded with a ring oscillator, which is readily injection-synchronized by the phases using multi-point injection. The key effect is that the ring oscillator corrects the phase error over process, voltage, and temperature variations. Furthermore, the use of the ring oscillator enables synchronization over a very large bandwidth, so that phase errors can be corrected over a wide frequency range.In other words, the combination of a multiphase generation followed by an injection-synchronized ring oscillator and a slope combiner enables, in particular, the generation of local oscillator signals that are used for frequency modulation with high harmonic suppression.

[0021] The following will refer to Fig. 3, Fig. 4 to Fig. Five examples of electronic circuits for implementing a phase generator, an injection-synchronized ring oscillator, and a combiner are described. The examples are shown for the case of a differential multiplier by a factor of three, i.e., N = 3. Naturally, the implementation can be extended to other multiplication factors as desired. Furthermore, it is clear that the corresponding electronic circuits could also be redesigned for processing asymmetric signals instead of differential signals.

[0022] In some examples, the phase generator can be implemented using a multiphase filter.

[0023] Fig. Figure 3 shows a schematic diagram of a poly-phase filter (PPF) capable of generating three differential phases spaced 120 degrees apart, which can be used to power the block for generating N differential phases 102 of the Fig. 2 to implement. In Fig. 3. LO,P and LO,N represent the two phases of a differential output signal of an oscillator, i.e., a phase difference between LO,P and LO,N is 180 degrees. The multiphase filter has two inputs and N = 3 differential outputs spaced 120 degrees apart. More precisely, the multiphase filter outputs a first differential signal Vout,0 and Vout,180 at a first differential output, a second differential output signal Vout,120 and Vout,300 at a second differential output, and a third differential output signal Vout,240 and Vout,60 at a third differential output. There is a phase shift of 120 degrees between any two of the differential output signals. As in Fig. As shown in 3, the multiphase filter is implemented using resistors and capacitors, which are based on the in Fig. The three ways shown are connected to each other.

[0024] Fig. Figure 3 shows a single-stage multiphase filter. In examples from the present disclosure, the use of a single-stage multiphase filter is sufficient, since phase errors are subsequently corrected using the injection-synchronized ring oscillator.

[0025] In other examples, a multi-stage PPF filter can be used to implement the phase generator. In other examples, a different circuit capable of generating N phases can be used, for example, a phase shifter with multiple taps.

[0026] Fig. Figure 4 shows a schematic view of a differential ring oscillator stage. The number of ring oscillator stages depends on N. In the case of N = 3, three differential stages (cells) of the Fig. 4. The ring oscillator. In each stage, terminals rP and rN are connected to output terminals outP and outN of the previous stage, so that the stages are connected in a ring. The differential output signal of the ring oscillator stage is output at terminals outP and outN. Terminals injP and injN represent a differential injection input to the ring oscillator stage. The differential input, i.e., injP and injN, is in Fig. 3 connected to a differential output of the phase generator, e.g. Vout,0 and Vout,180.

[0027] As in Fig. As shown in Figure 4, the ring oscillator stage comprises injection transistors 120 and 122, inverter transistors 124 and 126, and a load formed by load transistors 128 and 130. The drain terminals of inverter transistor 124 and injection transistor 120 are connected to the outP terminal of the ring oscillator stage's differential output. The drain terminals of inverter transistor 126 and injection transistor 122 are connected to the outN terminal of the ring oscillator stage's differential output. The source terminals of inverter transistors 124 and 126 are connected to a reference potential (e.g., ground) via a first current limiter, Iring. The source terminals of injection transistors 120 and 122 are connected to a reference potential, such as ground, via a second current limiter, linj. The current limiters Iring and linj can be formed by current sources and provide bias currents for the ring oscillator stage, i.e.Preload currents for a ring current of the ring oscillator and for an injection current of the respective stage.

[0028] The gate terminals of inverter transistors 124 and 126 are connected to terminals rP and rN, respectively. The gate terminals of injection transistors 120 and 122 are connected to terminals injP and injN, respectively.

[0029] The load formed from transistors 128 and 130 is connected between a voltage source Vdd and the drain terminals of the injector transistors and inverter transistors.

[0030] Transistors 128 and 130 constitute a load, with source terminals of the load transistors connected to the voltage source Vdd, a drain terminal of the load transistor 128 connected to the drain terminal of the inverter transistor 124, a drain terminal of the load transistor 130 connected to the drain terminal of the inverter transistor 126, a gate terminal of the load transistor 128 connected to the drain terminal of the load transistor 130, and the gate terminal of the load transistor 130 connected to the drain terminal of the load transistor 128.

[0031] Multipoint ring injection is achieved by applying each distinct output signal of the phase generator to a differential control input of a distinct ring oscillator stage, where the Fig. The differential control input shown in Figure 4 is formed by terminals injP and injN, which are connected to the gate terminals of the injection transistors 120 and 122. Thus, the injection transistors 120 and 122 of a respective ring oscillator stage are controlled by a differential output of the phase generator.

[0032] In other examples, alternative ring oscillator stages can be used, for example, ring oscillator stages that have a resistive load instead of a live load, or ring oscillator stages with / without tail current generators and the like.

[0033] Thus, according to examples in the present disclosure, each stage of the injection-coupled ring oscillator has an injection transistor configured to inject an injection current into the stage, wherein the phase generator output coupled to the stage is coupled to the control terminal of the injection transistor.

[0034] In examples of the present disclosure, the combiner is an edge combiner configured to combine the edges of the outputs of the ring oscillator stages to form the output signals. In examples, the edge combiner comprises a set of transistors, wherein each of the output signals of the injection-synchronized ring oscillator is coupled to the control terminal of another transistor in the set, the first terminals of the transistors in the set being coupled to a common voltage source and the second terminals of the transistors in the set being coupled to a reference potential.

[0035] A schematic diagram of such a flank combiner is shown in Fig. Figure 5 shows that the edge combiner comprises transistors 140, 142, 144, 146, 148, and 150. The source terminals of transistors 140 to 150 are connected to a reference potential, such as ground. The drain terminals of transistors 140, 142, and 144 are connected to a first terminal 152 of a differential output of the edge combiner, and the drain terminals of transistors 146, 148, and 150 are connected to a second terminal 154 of a differential output of the edge combiner. Furthermore, the differential outputs of the edge combiner are coupled to a common voltage source via a center tap of an inductor 162. In other examples, terminals 152 and 154 can be connected via a parallel resonant circuit, such as... B. an LC parallel resonant circuit or an RLC parallel resonant circuit coupled to the common voltage source 160.In other examples, there may be two current sources, one connected to transistors 140, 142, 144, and another connected to transistors 146, 148, 150.

[0036] The gate terminals of transistors 140 to 150 represent differential inputs of the edge combiner; that is, terminals r,0 and r,180 represent a first differential input, terminals r,120 and r,300 represent a second differential input, and terminals r,240 and r,60 represent a third differential input. Each differential input of the edge combiner is coupled to the differential output of a ring oscillator stage. In other words, signals at terminals r,i (i = 0, 60, 120, 180, 240, 300) are the outputs of the ring oscillator. The edge combiner combines the edges of the signals at terminals r,i in the current domain, thus generating at its output 152, 154 a signal whose frequency is N times the frequency of the input signals.

[0037] In other examples of the edge combiner, a common-gate architecture or a common-drain architecture can be used instead of a common-source architecture (source circuit architecture). In other examples, a differential current can be used for the edge combiner.

[0038] In the examples described, the transistors are implemented using field-effect transistors. In the case of a field-effect transistor, the gate terminal forms a control terminal, the drain terminal forms a first terminal, and the source terminal forms a second terminal. In other examples, the transistors can be implemented using bipolar transistors, where the base terminal forms a control terminal, the collector terminal forms a first terminal, and the emitter terminal forms a second terminal.

[0039] Examples of this disclosure can be applied to radar and communication systems where the frequency output by a local oscillator is to be multiplied to achieve a desired carrier frequency. For emission masking and up / down conversion of unwanted signals, it is advantageous to have a multiplier with a high harmonic blocking ratio. Examples of this disclosure enable enhanced harmonic blocking at the output of a frequency multiplier. At a system level, examples of this disclosure enable a more precise specification of harmonic blocking.Examples of this disclosure consist of a cascade of a stage that generates N phases with low loss and in a narrowband manner, followed by a ring oscillator that corrects phase errors over power, voltage, and temperature variations and over a wide frequency range, and then by an edge combiner. Thanks to the preceding two stages, the edge combiner is able to combine the N signals, which have equal phase intervals, to generate a harmonic at its output at N times the input frequency with high harmonic suppression. In examples of this disclosure, the phase generator is implemented using a single-stage polyphase filter with reduced losses compared to multi-stage polyphase filters.This avoids losses that would result from using filters with a higher number of stages or a larger bandwidth, which would need to be restored before the edge combiner with costly, power-consuming buffers.

[0040] Examples in the present application provide a method for frequency multiplication as described in Fig. Figure 6 shows that, at 200, versions of an oscillation signal are generated that are phase-shifted relative to each other. At 202, a ring oscillator is subjected to multi-point injection synchronization using the generated versions of the oscillation signal. At 204, output signals from stages of the ring oscillator are combined into an output signal whose frequency is a multiple of the frequency of the oscillation signal.

[0041] In some examples, the method involves generating the oscillation signal with a varying frequency. In others, the method involves generating N versions of the oscillation signal that are phase-shifted by 360 degrees / N relative to each other, injection-synchronizing N ring oscillator stages with the generated versions of the oscillation signal, and combining the output signals of the N ring oscillator stages to produce the output signal whose frequency is N times the frequency of the oscillation signal. In some examples, the signal involves generating versions of the oscillation signal by applying the oscillation signal to a multiphase filter.In examples, combining output signals from stages of the injection-synchronized ring oscillator involves applying the output signals to an edge combiner configured to combine the edges of the ring oscillator stage output signals into the output signal. In examples, multi-point injection synchronization of the ring oscillator involves applying each generated version of the oscillation signal to a control terminal of an injection transistor of each ring oscillator stage. In examples of the method of the present disclosure, the oscillation signal is a differential signal, the generated versions of the oscillation signal are differential signals, and the output signal is a differential output signal.

[0042] Although some aspects have been described as features related to a device, it is understood that such a description can also be considered a description of corresponding features of a method. Although some aspects have been described as features related to a method, it is understood that such a description can also be considered a description of corresponding features relating to the functionality of a device.

[0043] In the preceding detailed description, it can be seen that, for the purpose of streamlining the disclosure, various features have been grouped together in the examples. This method of disclosure should not be interpreted as reflecting an intention that the claimed examples require more features than are expressly stated in each claim. Rather, as the following claims demonstrate, the subject matter of the invention may be contained in fewer than all features of a single disclosed example. Thus, the following claims are hereby incorporated into the detailed description, with each claim being able to serve independently as a separate example.Although each claim can stand alone as a separate example, it should be noted that, while a dependent claim may refer to a specific combination with one or more other claims, other examples may include a combination of the dependent claim with the subject matter of any other dependent claim, or a combination of any feature with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. Furthermore, it is intended to include features of a claim in any other independent claim, even if that claim is not directly dependent on the independent claim.

[0044] The examples described above serve only to illustrate the principles of this disclosure. It is understood that modifications and variations of the arrangements and details described herein will be obvious to other people skilled in the art. Therefore, it is intended that any limitation is limited only by the scope of protection of the following patent claims and not by the specific details set forth herein by way of description and explanation of the examples. Reference symbol list 10 VCO 12 Output signal of the VCO 14 Frequency Multipliers 16 Output signal of the frequency multiplier 18 bandpass filter stages 20 Output of the bandpass filter stage 22 Injection synchronization stage 24 Output of the injection synchronization stage 50-phase generator 52 injection-synchronized ring oscillator 54 Combiners 56 Oscillation signal 60, 62, 64 phase generator outputs 70, 72, 74 ring oscillator stages 78 Output signal 80 Oscillator 100 frequency multipliers 102 Phase generation block 104 Ring oscillator 106 differential flank combiners 108 Output of the frequency multiplier 120, 122 injection transistors 124, 126 Inverter transistors 128, 130 load transistors 140 to 150 transistors of the edge combiner 152, 154 Connections of the differential output of the edge combiner 160 common voltage source 162 Inductor

Claims

[1] A frequency multiplier which has the following features: a phase generator (50, 102) configured to receive an oscillation signal (56) and to provide phase-shifted versions of the oscillation signal (56) at phase generator outputs (60, 62, 64); an injection-synchronized ring oscillator (52, 104) having a plurality of stages (70, 72, 74), wherein each of the phase generator outputs (60, 62, 64) is coupled to a different stage of the plurality of stages (70, 72, 74) for the purpose of multi-point injection, and a combiner (54, 106) configured to combine output signals of the plurality of stages (70, 72, 74) of the injection-synchronized ring oscillator (52, 104) into a signal (78) whose frequency is a multiple of a frequency of the oscillation signal (56). [2] The frequency multiplier according to claim 1, wherein the phase generator (50, 102) has N phase generator outputs, wherein the generated versions of the oscillation signal (56) are phase-shifted relative to each other by a phase shift of 360° / N, wherein the injection-synchronized ring oscillator (52, 104) has N stages, and wherein the output signal has a frequency that is N times a frequency of the oscillation signal (56), where N is an integer equal to or greater than two. [3] The frequency multiplier according to claim 1 or 2, wherein the phase generator (50, 102) comprises a multiphase filter. [4] The frequency multiplier according to any one of claims 1 to 3, wherein the combiner (54, 106) is an edge combiner configured to combine the edges of the output signals of the ring oscillator stages (70, 72, 74) to the signal (78) whose frequency is a multiple of a frequency of the oscillation signal (56). [5] The frequency multiplier according to claim 4, wherein the edge combiner comprises a set of transistors (140 - 150), wherein each of the output signals of the injection-synchronized ring oscillator (52, 104) is provided to a control terminal of a respective other of the set of transistors (140 - 150), wherein first terminals of the transistors of the set of transistors (140 - 150) are coupled to a common voltage source (160) and second terminals of the transistors of the set of transistors (140 - 150) are coupled to a reference potential. [6] The frequency multiplier according to any one of claims 1 to 5, wherein each stage of the plurality of stages (70, 72, 74) has an injection transistor (120, 122) configured to inject an injection current into the stage (70, 72, 74), and each phase generator output (60, 62, 64) is coupled to the control terminal of a respective injection transistor (120, 122). [7] The frequency multiplier according to any one of claims 1 to 6, wherein the oscillation signal (56) is a differential signal, the phase generator (50, 102) is a differential phase generator, the phase generator outputs (60, 62, 64) are differential phase generator outputs, the injection-synchronized ring oscillator (52, 104) is a differential injection-synchronized ring oscillator and the combiner (54, 106) is a differential combiner. [8] The frequency multiplier according to claim 7, wherein Each stage (70, 72, 74) of the injection-synchronized ring oscillator (52, 104) has a first and a second injection transistor (120, 122), a first and a second inverter transistor (124, 126) and a load (128, 130), first terminals of the first inverter transistor (124) and the first injection transistor (120) are connected to a first terminal (outP) of a differential output of the stage (70, 72, 74), first terminals of the second inverter transistor (126) and the second injection transistor (122) are connected to a second terminal (outN) of the differential output of the stage (70, 72, 74), The second terminals of the first and second inverter transistors (124, 126) are connected to a reference potential via a first current limiter (Iring). The second terminals of the first and second injector transistors (120, 122) are connected to the reference potential via a second current limiter (linj), the load (128, 130) is connected between a voltage source (Vdd) and the first terminals of the first and second inverter transistors (124, 126), a control terminal of the first inverter transistor (124) is connected to a first terminal of a differential output of another stage (70, 72, 74) of the injection-synchronized ring oscillator (52, 104), a control terminal of the second inverter transistor (126) is connected to a second terminal of the differential output of the other stage (70, 72, 74) of the injection-synchronized ring oscillator (52, 104), and The control terminals of the first and second injector transistors (120, 122) are connected to a differential output of the differential phase generator circuit (50, 102). [9] The frequency multiplier according to claim 8, wherein the load (128, 130) has a first and a second load transistor (128, 130), a first terminal of the first load transistor (128) is connected to the first terminal of the first inverter transistor (124), a first terminal of the second load transistor (130) is connected to the first terminal of the second inverter transistor (126), second terminals of the first and second load transistors (128, 130) are connected to the voltage source (Vdd), a control terminal of the first load transistor (128) is connected to the first terminal of the second load transistor (130), and a control terminal of the second load transistor (130) is connected to the first terminal of the first load transistor (128). [10] A signal generator comprising a frequency multiplier according to any one of claims 1 to 9 and an oscillator (80) configured to generate the oscillation signal (56). [11] The signal generator according to claim 10, wherein the oscillator (80) is a voltage-controlled oscillator configured to generate the oscillation signal (56) with a variable oscillation frequency. [12] A frequency multiplication method comprising the following steps: Generating (200) versions of an oscillation signal (56) that are phase-shifted relative to each other; Multipoint injection synchronization (202) of a ring oscillator (52, 104) using the generated versions of the oscillation signal (56), and Combining (204) output signals from stages (70, 72, 74) of the ring oscillator (52, 104) to a signal (78) whose frequency is a multiple of a frequency of the oscillation signal (56). [13] The method according to claim 12, which further comprises generating the oscillation signal (56) with a varying frequency. [14] The method according to claim 12 or 13, comprising generating (200) N versions of the oscillation signal (56) which are phase-shifted relative to each other by a phase shift of 360° / N, injection synchronizing N ring oscillator stages (70, 72, 74) with the generated versions of the oscillation signal (56), and combining output signals of the N ring oscillator stages (70, 72, 74) to the signal (78) whose frequency is N times the frequency of the oscillation signal (56). [15] The method according to claim 14, wherein the generation (200) of versions of the oscillation signal (56) comprises applying the oscillation signal (56) to a multiphase filter. [16] The method according to claim 14 or 15, wherein the combining (204) of output signals from stages (70, 72, 74) of the injection-synchronized ring oscillator (52, 104) comprises applying the output signals to an edge combiner configured to combine the edges of the output signals of the ring oscillator stages (70, 72, 74) to form the signal (78). [17] The method according to one of claims 13 to 16, wherein the multi-point injection synchronization (202) of the ring oscillator (52, 104) comprises applying a respective generated version of the oscillation signal (56) to a control terminal of an injection transistor (120, 122) of a respective ring oscillator stage (70, 72, 74). [18] The method according to any one of claims 13 to 17, wherein the oscillation signal (56) is a differential signal, wherein the generated versions of the oscillation signal (56) are differential signals and wherein the signal (78), whose frequency is N times the frequency of the oscillation signal (56), is a differential signal.

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